Problem: Express your answer as a mixed number simplified to lowest terms. $15\dfrac{18}{20}-10\dfrac{2}{4} = {?}$
Solution: Separate the whole numbers from the fractional parts: $= {15} + {\dfrac{18}{20}} - {10} - {\dfrac{2}{4}}$ Bring the whole numbers together and the fractions together: $= {15} - {10} + {\dfrac{18}{20}} - {\dfrac{2}{4}}$ Subtract the whole numbers: $=5 + {\dfrac{18}{20}} - {\dfrac{2}{4}}$ Simplify each fraction: $= 5 + {\dfrac{9}{10}} - {\dfrac{1}{2}}$ Find a common denominator for the fractions: $= 5+\dfrac{9}{10}-\dfrac{5}{10}$ Subtract the fractions: $= 5+\dfrac{4}{10}$ Combine the whole and fractional parts into a mixed number: $= 5\dfrac{4}{10}$ Simplify to lowest terms: $= 5\dfrac{2}{5}$